This invention is directed to communications over an electrical distribution network or the like, employing a communications system known as TWACS®, and more particularly, to a very rapid polling system for use in the detection and mapping of power outages.
Efficient outage detection and mapping is an important concern of electric utilities. In situations where a power outage occurs, the utility needs to quickly find out a) that an outage has occurred, b) where the outage has occurred, and c) the extent of the outage. This enables the utility to then marshal and direct the resources necessary to correct the outage and restore power in the shortest possible time.
Using current TWACS protocols to determine the presence or absence of an individual meter on the network requires both an outbound command and an inbound response which currently includes a minimum of 3 bytes of information. While a reasonable level of outage mapping is obtainable at this relatively slow polling rate (by carefully selecting a subset of meters on different buses, feeders, and phases), it would be beneficial to have an alternate means of polling all the units on a substation, in order to locate even very small outages (i.e., a single meter) in a very short period of time. It would be particularly helpful, given the size of many distribution networks, to be able to poll a group of which included thousand of meters on the order of 1-2 minutes.
One possible solution to this problem would be to have each meter in a group sequentially respond to a poll command. This would require a message length of only one or two pulses per meter to achieve a desired polling rate. By having a very large group of meters sequentially respond to a single outbound command, this would minimize the overhead of outbound commands, and meters could be polled at a rate of approximately nearly 1 pulse for each half-cycle of the 60 Hz waveform.
A problem with this approach is the reliable detection of the pulse(s) in the high noise environment of a power line. One way to overcome this difficulty would be to increase the power of the pulses transmitted by each meter. But this would mean overriding the pre-set firing angle established within the TWACS to generate the much stronger current pulse. This, in turn, creates the additional problem of increasing the stress on the electronics in the meter. It is also unclear as to how large a current pulse could be generated before reaching the saturation point in a service transformer, and the other effects this would have on the power line local to that transformer.